The present invention relates to a rotary press to lay patterns of a material on a strip material, including a working cylinder carrying embossing plates of the patterns on the aforesaid material to be laid and an anvil cylinder, means to rotate the working cylinder, means to heat and control the temperature of this working cylinder, means to exert a defined prestress between the working cylinder and the anvil cylinder and free bearing means between the anvil cylinder and its pivoting shaft
The advantage of this type of press in contrast with flat stamping lays in the ability to work constantly with a perceptible faster speed than during the flat stamping process. The gas resulting from the vaporization of the wax that is located between the polyester support strip and the metal embossing plate of the strip material is discharged in an easier way and the consumption of strip material to be laid can be perceptibly reduced. This material, generally made of a laminated compound of four layers, a polyester support strip, a layer of wax, a metallic embossing plate and a layer of glue, is expensive.
To allow a reduction of the consumption of strip material to be laid in an optimal way, it is not only necessary to use a rotary press but the strip material should not cross the rotary press according to the standard path, but in an almost linear path. Indeed, during the standard path, the strip material to be laid and the support strip on which the pattern of the material has been laid, stay one touching the other and are pressed against the anvil cylinder upon a given angle of this anvil cylinder after being passed through the cylinders of the rotary press to increase the time of contact and facilitate the fixing of the pattern laid on the support strip. This standard process of passage perceptibly limits the saving possibilities of the strip material to be laid because the support strip and the strip material have to move simultaneously.
To allow an optimal saving of the consumption of strip material, one should be able to stop, or even withdraw a certain length of the strip material between two pattern deposits on the support strip. This is only possible if the strip material to be laid and the support strip are almost only in contact over a line corresponding to the respective contact lines between the two cylinders of the rotary press, or at the very least over a small enough lengthwise distance of the strip support to allow a related displacement as soon as they are not pinched anymore between the cylinders of the press, in other words between two successive transfers of the patterns on the support strip. This is only possible if the strip material to be laid has an almost linear path.
Taking into consideration the constraints and in particular the very short time of contact between the strip material to be laid and the support strip, the average temperature of the working cylinder of the rotary press has to be higher and the allowable temperature deviations are smaller than in flat stamping and in a rotary press with standard path, mentioned above.
In order to satisfy this very low level of tolerance, it is not only necessary to precisely control temperatures, but it is also indispensable that the exerted pressure between the press cylinders and the space between these cylinders that allows the simultaneous passage of the support strip, the strip material with the pattern to be laid and the embossing plates, be precisely adjusted, avoiding that the adjustment of one of these two parameters exercise an influence on the other. It is also important that the space between the cylinders crossed by the support strip, the strip material and the embossing plate be kept constant and not vary when the temperature of the working cylinder increases.